Flavored slush snacks enjoy a high level of acceptance, particularly by children in the six to twelve year old age group. These confections are commonly available for consumption at or near the place of production, and are prepared by a scraped-surface freezer, similar to those used for making soft ice cream. The flavored slush snacks are served at or near the freezing point of water and are composed of a sweetened and flavored aqueous liquid containing a substantial quantity of fine ice crystals. They are commonly prepared on a continuous basis with constant agitation during freezing. It is generally impractical to prepare such compositions in the home because of the specialized equipment required. As a further disadvantage, it is noted that once products of this nature made with scraped surface freezers are melted, re-freezing of the product provides an undesirable product which is essentially a block of ice.
Several recent attempts to provide slush snacks that can be prepared or stored in a home freezer are found in the patent literature. U.S. Pat. No. 3,826,829 to Marullick describes a liquid suitable for producing a slush beverage which utilizes a composition containing water, sugars, polyols, flavor, and coloring agents together with pectin in combination with other gums as a stabilizing agent. The product of this invention, which can include both carbonated and non-carbonated aqueous solutions as a base, has for an object the provision of a product having a sherbet-like consistency. This fine grained ice crystal structure is a disadvantage where products containing "shale" ice crystals are desired. In addition, the pectin imparts an unpleasant, somewhat slimy characteristic to the beverage when the product has melted and also contributes to haziness in the product, which can be unacceptable for purposes where clarity is desired.
U.S. Pat. No. 3,897,571 to Homler et al. describes a process for producing a refrigeration-stable slushed comestible concentrate that is spoonable and stirrable at 0.degree. F., and which remains in this desirable condition over an extended period of storage at home freezer temperatures, without hardening into an unspoonable block. The process includes the steps of slowly growing ice crystals in a composition containing gum and sugar and continuing the crystallization process while agitating to produce an overrun and to incorporate a gaseous phase to establish a stable tertiary phase mixture of concentrated syrup matrix interspersed with coarse ice crystals in a gaseous foam. A product of this type has the disadvantage of requiring distribution and storage only under home freezer temperatures. In addition, it does not retain its desirable characteristics through a thaw-refreeze cycle.
U.S. Pat. No. 3,647,472 to Speech et al. describes a beverage mix which can be stored at room temperature for an indefinite period of time but which is intended to be placed in a home freezer to be allowed to freeze to a slush consistency before it is consumed. The beverage mix is intended to be combined with an alcoholic distillate or other liquid ingredient before consumption. The composition contains sugar in quantities up to 30-40% by weight, which serves as both a sweetener and as a cryoscopic modifier. Glycerol is also used as a cryoscopic modifier, for the purpose of controlling the size of the ice crystals and the freezing point of the mix.
One disadvantage of the Speech et al. product is the requirement that it be mixed with another liquid, such as an alcoholic distillate or other beverage, before consumption. In addition, the patented product contains glycerol at a level of 0.5 to 8% to control the size of the ice crystals formed during freezing. It has been found that glycerol contributes an undesirable bitter flavor to the product.
U.S. Pat. No. 3,922,361 to Vann describes a process for preparing a soft frozen, all natural fruit juice in which a fruit juice concentrate, such as orange, is thawed and combined with natural sweeteners and subjected to freezing in a slush freezing apparatus.
A number of problems are encountered in preparing a flavored liquid snack product which is intended to be marketed in containers stored at room temperature for subsequent use by the household by placing the container in a home freezer. The first problem is one of sweetness regulation. In most compositions of this nature, the presence of a high level of sugar is desired to modify the extent and type of ice crystal formation sufficiently to permit the realization of a slush rather than a solid frozen product. Slush is defined as a mixture of liquid and ice crystals. Thus, the selection of a suitable sugar or combination of sugars which will supply the desired ice crystal modification effect and freezing point depression and at the same time not be unbearably sweet to the taste is important.
A second and related problem is that of crystallization of dextrose or other sugars used in preparing these products. Because of the concentration effect which takes place on freezing of liquids of this nature, sugars such as dextrose reach a point where they are in supersaturated solution, whereupon crystallization of the sugar takes place. The crystals do not readily re-dissolve on thawing of the product. The presence of crystallized dextrose and other sugars is decidedly a disadvantage in slush snacks in that the white crystals provide an unattractive, undesirable, appearance to the frozen product. This problem of crystallization is accentuated where repeated freeze-thaw cycles are encountered.
Another important consideration is the shelf stability of the liquid product at room temperature. Liquids having a high sugar content are ideal places for microorganisms such as yeast to grow. It is thus important that microbiological stability is insured by using the correct balance of sugar concentration, acidity and added preservatives such as the sorbates and benzoates.
Still another important consideration is the nature of the final product. It is desirable to provide a product which has a substantial proportion of platelet ice crystals, termed "shale" ice, intermixed with liquid and fine ice crystals to form a homogenous mass. This homogenous mass must form during quiescent freezing of the product in the container. At the same time, the frozen product must be easily disrupted by stirring or by pressure exerted by deforming a flexible container.
Another important consideration is that the consistency of the slush product remain substantially unchanged over a prolonged period of storage at freezer temperatures. Home freezer temperatures vary from +10.degree. F. to -10.degree. F. and the product must be formulated so that the product is readily stirred to a slush with a spoon after two to three months storage at -10.degree. F.
Still another important consideration is the character of the slush snack after removal from the freezer and during consumption. It is highly desirable that immediately upon removal from the freezer, the product can be simply stirred with a spoon to break it up into a slush which is readily consumable with a spoon. During melting of this slush, which should take place over a period of about 15-30 minutes at room temperature, desirable slush characteristics should be maintained. The completely melted product should also be suitable for drinking, should be free from gummy or slimy characteristics and should have a consistency approaching that of water.